MongoDb: support `3.x.x` driver

[enricobenedos]

What would you like to be added:
As per title, add support to Mongo driver V3.

Why is this needed:
To avoid runtime exceptions like:

File name: 'MongoDB.Driver.Core, Version=2.28.0.0, Culture=neutral, PublicKeyToken=94992a530f44e321'
   at HealthChecks.MongoDb.MongoDbHealthCheck.CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken)
   at Microsoft.Extensions.Diagnostics.HealthChecks.DefaultHealthCheckService.RunCheckAsync(HealthCheckRegistration registration, CancellationToken cancellationToken)
[10:16:56 ERR] Health check mongodb threw an unhandled exception after 0.7158ms
System.IO.FileNotFoundException: Could not load file or assembly 'MongoDB.Driver.Core, Version=2.28.0.0, Culture=neutral, PublicKeyToken=94992a530f44e321'. The system cannot find the file specified.

[eerhardt]

This was done in #2324. We are preparing a v9 release of HealthChecks that will include this support.

This is a duplicate of #2322.